Insulation module with superposed deformed core sheets

ABSTRACT

Insulation modules having a core of relatively movable, flat and corrugated metal sheets assembled between opposed faceplates and having deformable, seal-forming portions projecting beyond the faceplates. Methods of fabricating such modules and of forming them into modular insulation assemblies.

finite Seams ateni firemen [4 1 Jan. 25, 1972 54] HNSULATION MODULE WITH3,054,524 9/1962 Casten ..220/|5 SUPERPOSED DEFORMED CORE 3,151,71210/1964 Jackson SHEETS 3,190,412 9/1965 Putter et a1. 3,212,861 10/1965Whitesides ..52/410 [72] Inventor: George D. Cremer, Lemon Grove, Calif.FORE'GN PATENTS OR APPLICATIONS [73] Assignee: The United States ofAmerica as represented by the United States Atomic 66886O 8/963 CanadaEnergy Commision 891,353 3/1962 Great Britain 609,625 9/1960 Italy [22]Filed: Aug. 10, 1964 Primary Examiner-Frank L. Abbott [2H Appl' 388548Assistant Examiner-Alfred C. Perham A!l0rneyRo1and A. Anderson [52] US.Cl ..52/509, 52/249, 52/573,

52/618, 52/40'4, 176/87 [57] ABSTRACT [221;] ..E04b 2/44, 1304b 1/78Insu'ation modules having a core of relatively movable flat I l 0 5 fand corrugated metal sheets assembled between opposed ,6 5 9 Q 3 ffaceplates and having deformable, seal-forming portions pro- IS D 1 5220/9 9 A jecting beyond the faceplates. Methods of fabricating such thd 1 1 t' [56] References Cited Ehoiules and of forming em into mo u armsu a 1011 assem UNITED STATES PATENTS 11 Claims, 10 Drawing Figures2,482,618 9/1949 Hosbein ..52/573 X STEAM INVENTOR GEORGE DORLA/VD CREMEBY M7$MQM ATTORNEYS PATENTEU JANZS 19. 2

SHEET & 0F 6 INVENTOR GEO/75E DORLAND CREME ATTORNEYS PATENTED M25 19723.836374 SHEET 5 [IF 6 I NVENT OR GEORGE DORLAND CREMEH BY /M 9MATTORNEY.)

PATENTED mes 1972 SHEET 6 UF 6 GEORGE DORLAND CREME R ATTORNEYSINSULATION MODULE WITH SUPERPOSED DEF ORMED CORE SHEETS STRUCTURE ANDMETHOD This invention relates generally to thermal insulation, moreparticularly to metal insulation, and, specifically, to sandwichtypeinsulation modules and assemblies thereof.

The novel insulation modules and modular assemblies provided inaccordance with the principles of the present invention are particularlyuseful for providing internal thermal insulation for gas-cooled nuclearreactors and associated plumbing. However, the novel insulation modulesand modular assemblies provided by the present invention are by no meansuseful only in this particular application, but may be advantageouslyutilized wherever thermal insulation is required. Therefore, althoughthe advantages and principles of the present invention will be developedby reference to this particular application, it is to be understood thatthe ensuing description is not intended to limit the scope of thepresent invention.

Nuclear reactors offer a good but as yet unrealized potential for theefficient and economical production of electrical power from fissionablematerials; One reason that reactors have not yet proved economical isthe expense of constructing the reactor. The reactor must be capable ofwithstanding the high temperatures generated in the fission reaction andmust be resistant to radiation damage; and, to provide a reactor withthese capabilities, it has heretofore been necessary to fabricate itfrom expensive alloys, adding materially to its initial cost. Thepresent invention solves this problem by providing novel insulationmodules and modular assemblies for insulating the reactor from theradiation and heat given off in the fission process. As a result, thereactor may be fabricated from economical materials such as mild steelat a cost much lower than has heretofore been possible.

The novel modules of the present invention consist of a core ofjuxtaposed corrugated metal sheets held in an assembled relationshipwhich permits relative movement of the core sheets, making the modulecapable of withstanding stresses imposed by nonuniform heating.

A number of advantages are obtained by the novel module constructionjust described. For example, insulation modules constructed in accordwith the principles of the present invention will withstand years ofexposure to intense radiation at levels as high as 10 to 10 neutrons andgamma rays per square centimeter per second. Also, such modules are noteffected by mechanical vibration, rapid variations in the pressure inthe reactor, chemical corrosion, high temperatures, or thermalexpansion. In addition, the modules of the present invention may beeasily fabricated for and readily installed in or on reactors or otherstructures having a variety of flat, curved, cylindrical, and otherconfigurations.

From the foregoing, it will be apparent that one major object of thepresent invention is the provision of thermal insulation which isparticularly useful in gas cooled nuclear reactors.

Another important object of the present invention is the provision ofthermal insulation structure which is sufficiently radiation-damageresistant to withstand years of exposure at radiation levels on theorder of 10 to neutrons and gamma rays per square centimeter per second.

Yet another primary object of this invention is the provision of aninsulation structure which will not deteriorate from mechanicalvibration, pressure variation, chemical corrosion, or exposure tonuclear radiation.

Another important object of the present invention is the provision of aninsulation structure capable of withstanding rapid gas pressure changes.

Still another object of this invention is the provision of insulation inaccordance with the preceding object which will not contaminate thereactor gas or other atmosphere in which it is located.

Yet another object of this invention is the provision of insulationstructure with a low thermal conduction factor which is capable ofretaining its thermal properties over long periods of time inhigh-temperature environments.

Another object of the present invention is the provision of all-metalinsulation in modular form which may be rapidly and easily assembledinto or on structures having flat, curved, cylindrical, and otherconfigurations.

A further specific object of this invention is the provision ofinsulation modules having strength and structural integrity andaccommodating relative movement of core laminations and faceplatesrelative to each other to compensate for nonuniform thermal effects.

A related object is the provision of modules in which, upon assembly,the abutting edges of core laminations may be deformed to obtain a snugfit to maintain efficient insulating value in the seam area withouttransmitting shear loads between adjacent modules.

Another object of the present invention is the provision of novelmethods for fabricating insulation modules in accord with the precedingobjects.

Additional objects and further novel features of the present inventionwill become fully apparent from the appended claims and as the ensuingdetailed description and discussion proceeds in conjunction with theaccompanying drawing, in which:

FIG. 1 is a diagrammatic view of a plant employing a nuclear reactor ofthe type with which the novel insulation modules and modular assembliesof the present invention are particularly useful;

FIG. 2 is a vertical section through the reactor;

FIG. 3 is a perspective view of the interior of the upper portion of thereactor with a number of the insulation modules in place;

FIG. 4 is a perspective view of a portion of one form of novelinsulation module provided by the present invention;

FIG. 5 is a fragmentary view of one form of core sheet which may beemployed in insulation modules constructed in accord with the principlesof the present invention;

Flg. 6 is a perspective view of a jig for assembling the insulationmodules of the present invention;

FIG. 7 is an elevation, to an enlarged scale, of a number of modules andthe fasteners by which they are retained in position;

FIG. 8 is a perspective view of a hemispherical insulation module forthe upper end of the reactor;

FIG. 9 is a perspective view, to a reduced scale, of an alternate formof hemispherical insulation module; and

FIG. 10 is a cylindrical insulation module constructed in accord withthe principles of the present invention.

As indicated above, the novel insulation of the present invention isparticularly useful for insulating gas-cooled nuclear reactors and theassociated plumbing. As shown diagrammatically in FIG. 1, the atomicpile 22 (see FIG. 2) is housed in the reactor 20. A gas, commonlyhelium, is circulated through the reactor, where it is heated, and thenthrough a heat exchanger 24, where the hot gas converts water to steam.The steam is employed to drive a turbine 26 and is then condensed andrecirculated through heat exchanger 24.

Reactor 20, shown in more detail in FIG. 2, is normally fabricated froma cylindrical center section 28 and lower and upper hemispherical endsections 30 and 32 and is typically 35 feet in diameter and 45-50 feetlong. Heretofore, the center section 28 and lower end section 30 havebeen designed of 3- inch thick stainless steel and the upper end section(or hot dome) 32 of 5-inch thick stainless steel. Domes 30 and 32 areprovided with a gas inlet 34, a gas outlet 36, and access ports 38 forinstrumentation, control rods, fuel cells and the like for pile 22 whichis suspended in the center of reactor 20.

Reactor 20 is shielded by a 1-inch thick stainless steel liner orthermal barrier 40 which, as shown in FIG. 3, rests on an annular ledge41 at the lower end of the reactors center section 28. Liner 40 isparallel to and spaced from center section 28 and hot dome 32 of reactor20 and, as shown in FIG. 2, defines an annular channel for the flow ofcooling gas.

In accord with the present invention, the interior of liner 40 is linedwith a wall 42 constructed of insulation modules 44 of novelconstruction to thermally isolate reactor from atomic pile 22.Additional insulation modules are employed to insulate hot gas outlet 36and other plumbing of the reactor. Employing insulation as justdescribed makes it possible to fabricate reactor 20 from relativelyinexpensive mild steel instead of stainless steel as was heretoforenecessary, which is extremely important since it materially reduces thecost of the reactor.

Turning next to FIG. 3, the portion of insulation shell 42 attached tothe cylindrical lower portion of liner 40 consists of generallyrectangular insulation modules 44 which are typically 2 feet square and3 inches thick although these dimensions are not critical and may bevaried as the design requires.

Insulation modules 44, as shown in FIG. 4, each consist ofa pair ofparallel, spaced apart face plates 46 and 48 between which a core 50composed of a stack of superposed, embossed core sheets 52 issandwiched. Tie rods 54, extending through core 50 and fixed at theiropposite ends to face plates 46 and 48, maintain configural integrityofmodule 44.

Faceplates 46 and 48 might typically be 0.050-inch thick stainlesssteel. and core sheets 52 are preferably made from stainless steel foilhaving a thickness ranging from 0.001 to 0.01 inch.

Any suitable pattern may be embossed on the metal foil from which coresheets 52 are formed. The only important requirements are that thepattern selected: (I provide as little metal-to-metal contact aspossible between adjacent sheets; (2) divide the space between adjacentsheets into small pockets of relatively stagnant gas; and (3) provide asmall degree of communication between the pockets. Minimummetal-to-metal contact is desirable to minimize conductivity through themodule and thereby maximize its insulating properties. The division ofthe spaces between adjacent sheets into pockets in which the helium orother gas in the reactor is stagnant materially enhances the insulationproperties of the module as the stagnant gas transfers heat very slowlybetween adjacent core sheets.

Some degree of connection between the pockets is necessary to preventrapid pressure changes in the reactor from destroying the insulation.For example, pressurized reactors of the type described above maysuddenly he depressurized. In such circumstances, he communicationbetween the gas pockets in an insulation module facilitates gas flow andequilization of the pressure within the module and between the moduleand the reactor, preventing the imposition of unequal pressures on anddestruction ofthe module.

Referring now to FIG. 5, one type of core sheet 52 which may be used ininsulation modules of the type illustrated in FIG. 4 has a sawtoothlikeappearance, providing parallel, spaced-apart ridges 56 alternatelyvisible from opposite sides of the sheet. Ridges 56 are designed toprovide minimum contacting area when abutted against an adjacent sheet.It is not critical, however, that this particular form of core sheet beemployed as any core sheet having the characteristics described abovemay be used.

The insulation module 44 just described may be assembled in anyconvenient manner such as in the simple jig 70 illustrated in FIG. 6.This jig may be fabricated of any suitable material and includesspaced-apart bottom bars 71 for supporting the module, side members 72arranged in a rectangle having the same dimensions as the module, andvertically extending L-shaped guides 74 at the four corners of the jig.Bottom faceplate 48 is placed in jig 70 and a predetermined numberofcore sheets 52 are stacked on the bottom plate. The second faceplate46 is then placed on the core 50 comprised of the stacked core sheets 52and holes for tie rods 54 are pierced through faceplates 46 and 48 andcore 50. Piercing of the tie rod apertures is an important feature inthe assembly of modules 44 since this precludes contamination of core 50and the helium gas which it will later contact with metal chips, oil, orother foreign material as would be the case if the tie rod holes weredrilled or similarly formed.

Following the piercing operation, tie rods 54 are inserted into the tierod holes and the ends of the rods are upset and welded to faceplates 46and 48.

An important feature of the assembly process just described is that thepiercing operation is designed to develop a hole having a diameterslightly larger than that of the associated tie rod 54 to minimizecontact between the tie rod and the core sheet 52. This permits slightmovement of core sheets 52 relative to each other and to faceplates 46and 48, eliminating shear forces which would otherwise be exerted on themodule by nonuniform heating. Consequently, the novel insulation modulesof the present invention are not adversely affected by nonuniformheating.

Referring back to FIG. 4, core 50 of the insulation module 44 justdescribed is slightly larger than faceplates 46 and 48 so that coresheets 52 protrude beyond the faceplates. This feature is important inthe assembly of modules 44 to form the insulation shell or assembly 42shown in FIG. 2. Specifically, the insulation modules are dimensioned sothat, when fastened to liner 40 as shown in FIG. 3, there will be aslight interference fit between adjacent modules. Therefore, when themodules are assembled, the edges of the core sheets 52 of adjacentmodules deform against each other providing thermal and radiationsealing along the joints between adjacent modules. At the same time, thesealing arrangement prevents the transmission of shear loads betweenadjacent modules which is an important feature of the present inventionsince it prevents destruction of the shell by nonuniform heating,mechanical vibration, pressure changes, and the like.

Instead of employing the tie rods described above to assemble the coresheets and faceplates into self-sustaining modules and then fasteningthe modules to liner 40, the fastening arrangement shown in FIG. 7 maybe employed. Referring now to this figure, studs 76 may be welded orotherwise fixed to the inner surface of and oriented to extend inwardlyfrom liner 40. The modules, in the form of an unconnected assemblage ofcore sheets and faceplates, are then positioned against studs 76 andretained in place by washers 78 and nuts 80 threaded on studs 76. As inthe previously described arrangement, adjacent modules are designed tohave a slight interference fit when assembled to provide thermal andradiation sealing around studs 76 and along the joints between adjacentmodules without transmitting shear loads between adjacent modules.

The upper end of insulation shell 42 is generally hemisphericalinsulation module 82 as shown in FIG. 8. This module may advantageouslybe formed of the cross corrugated type of core sheet materialillustrated in FIG. 5 and discussed above because the latter is readilydeformable and has excellent drapability characteristics so that it canbe readily molded into hemispherical or other three-dimensionalcontours.

Module 82 is constructed by building a core 84 on a generallyhemispherical faceplate 86 (which may be of the same type of material asfaceplates 46 and 48 discussed above) from strips of foil which are cutand arranged in layers until the desired thickness of the core 84 isobtained.

A second faceplate 88 is arranged on top of core 84 and the twofaceplates interconnected with tie rods (not shown) in the mannerdescribed above in conjunction with modules 44. The necessary ports oropenings are formed in insulation module 82 at any time duringconstruction of the module, as by punching or cutting holes in eachsheet; and the assembled modules are attached to stainless steel liner40.

If the dome or other contoured vessel portion to be insulated is smalland relatively few ports are required, an alternate method offabricating the insulation module may be employed. Specifically, theouter faceplate is employed as a mold and a core is built up in themanner just described. However, as each layer of core sheet material isadded, the individual strips may be attached to those of the subjacentlayer as by poke welds. When the core has been built to the desiredthickness, the outer face plate is removed, leaving a selfsustainingmodule consisting of superposed layers of cross corrugated core sheetmaterial.

The hot gas outlet 36 from reactor 20 and other plumbing mayadvantageously be insulated with a cylindrical module 90 of the typeillustrated in FIG. 10. Referring now to the latter figure, module 90consists of concentric inner and outer sleeves 92 and 94 (preferably ofthe same material as faceplates 46 and 48) between which a core 96 issandwiched. Core 96 consists mainly of corrugated core sheets 98 which,as shown in FIG. 10, may have a simple sine wave cross-sectionalconfiguration.

Adjacent corrugated sheets 98 are separated by flat, unembossed coresheets 100 to prevent internesting of adjacent corrugated core sheets98. Tie rods as described above may be employed to fasten together theinner and outer sleeves 92 and 94, if necessary or desired. However, itmay not be necessary in many cases to employ tie rods as the frictionbetween the core sheets and the faceplates and adjacent core sheets willmaintain the structural integrity of the module.

Modules 90 can be fastened to the structure being insulated in the samemanner as the modules 44 and 82 described above, or, if the modulesurrounds and is supported by a pipe or the like, connections between itand the insulated structure may be unnecessary.

Although the illustrated cylindrical module 90 employs core sheets witha sine wave corrugation, it is not necessary that this particular typeof core sheet be employed; and, for some applications, it may beadvantageous to employ the type of core sheet illustrated in FIG. 5 anddescribed above or core sheets having still other forms ofconfigurations and the characteristics described above. Such.modifications are, therefore, to be understood as being within the scopeof the present invention as is the use of insulation produced in accordwith the principles of the present invention to insulate other thannuclear reactors. I

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent l. Aself-supporting insulation module, comprising:

a. a stack of superposed embossed core sheets having protuberancesseparating said sheets with a minimum of contact between adjacent sheetsand dividing the spaces between said sheets into small substantiallymutually isolated areas;

b. faceplates of sufficient thickness to be substantially rigid onopposite sides of said stack of core sheets;

c. means for holding said core sheets and said faceplates in assembledrelationship, said holding means permitting relative movement betweensaid plates and said core sheets in planes parallel to said sheets andpreventing movement therebetween in a direction perpendicular to saidplanes and said faceplates; said core sheets being fabricated ofadeformable material and, on at least one edge of the module, said coresheets protruding beyond the faceplates;

e. whereby the protruding portions of said core sheets can be deformedagainst a component adjacent said one edge of said module to provide aseal between said module and said component and to at least minimize thetransmission of shear loads between said module and said component.

2. A module as defined in claim 1, wherein said core sheets are of metalfoil.

3. A module as defined in claim 2, wherein said metal is stainless steeland said foil has a thickness in the range of 0.001 to 0.010 inch.

4. A module as defined in claim 1, wherein said holding means comprisestie members extending through said stack of core sheets, the ends ofsaid tie rods bein fixed to said faceplate and said tie membersextending t rough aligned apertures in said core sheets of larger areathan said tie member to permit movement of said core sheets relative toeach other and to said faceplates.

5. A module as defined in claim 1, wherein the faceplates are stainlesssteel.

6. A module as defined in claim 1, wherein said faceplates are on theorder of 0.050 inches thick.

7. A module as defined in claim 1, wherein the stack of superposed coresheets includes corrugated core sheets and flat core sheets distinctfrom and separating said corrugated sheets and cooperating with thecorrugations thereon to divide the spaces between adjacent sheets intosmall, substantially mutually isolated spaces.

8. Insulation for nuclear reactors and other structures, comprising:

a. plural insulation modules lining the portion of the structure to beinsulated, said modules each comprising a pair of faceplates and a stackof superposed core sheets sandwiched therebetween with the core sheetsprotruding beyond those edges of said plates which face adjacent modulesand terminating in edges spaced from said plate edges;

b. means for retaining said modules in position on said structureportion; and

c. adjacent modules being disposed with their terminal edges incompressive abutting relationship establishing an interfering fitbetween said terminal edges and thereby ef fectively sealing the seamsbetween adjacent modules while minimizing the transmission of shearloads between the modules.

9. Insulation as defined in claim 8, said modules being selfsupportingand including means for holding said core sheets and said faceplates inassembled relationship, said holding means permitting relative movementbetween said plates and said core sheets in planes parallel to saidsheets and preventing movement therebetween in a direction perpendicularto said planes and said faceplates.

10. Insulation as defined in claim 8, wherein said core sheets are ofmetal foil.

11. Insulation as defined in claim 8, wherein the stack of core sheetsincludes corrugated core sheets and flat core sheets separating saidcorrugated core sheets and cooperating with the corrugations therein todivide the spaces between adjacent sheets into small, substantiallymutually isolated spaces.

1. A self-supporting insulation module, comprising: a. a stack ofsuperposed embossed core sheets having protuberances separating saidsheets with a minimum of contact between adjacent sheets and dividingthe spaces between said sheets into small substantially mutuallyisolated areas; b. faceplates of sufficient thickness to besubstantially rigid on opposite sides of said stack of core sheets; c.means for holding said core sheets and said faceplates in assembledrelationship, said holding means permitting relative movement betweensaid plates and said core sheets in planes parallel to said sheets andpreventing movement therebetween in a direction perpendicular to saidplanes and said faceplates; d. said core sheets being fabricated of adeformable material and, on at least one edge of the module, said coresheets protruding beyond the faceplates; e. whereby the protrudingportions of said core sheets can be deformed against a componentadjacent said one edge of said module to provide a seal between saidmodule and said component and to at least minimize the transmission ofshear loads between said module and said component.
 2. A module asdefined in claim 1, wherein said core sheets are of metal foil.
 3. Amodule as defined in claim 2, wherein said metal is stainless steel andsaid foil has a thickness in the range of 0.001 to 0.010 inch.
 4. Amodule as defined in claim 1, wherein said holding means comprises tiemembers extending through said stack of core sheets, the ends of saidtie rods being fixed to said faceplates and said tie members extendingthrough aligned apertures in said core sheets of larger area than saidtie member to permit movement of said core sheets relative to each otherand to said faceplates.
 5. A module as defined in claim 1, wherein thefaceplates are stainless steel.
 6. A module as defined in claim 1,wherein said faceplates are on the order of 0.050 inches thick.
 7. Amodule as defined in claim 1, wherein the stack of superposed coresheets includes corrugated core sheets and flat core sheets distinctfrom and separating said corrugated sheets and cooperating with thecorrugations thereon to divide the spaces between adjacent sheets intosmall, substantially mutually isolated spaces.
 8. Insulation for nuclearreactors and other structures, comprising: a. plural insulation moduleslining the portion of the structure to be insulated, said modules eachcomprising a pair of faceplates and a stack of superposed core sheetssandwiched therebetween with the core sheets protruding beyond thoseedges of said plates which face adjacent modules and terminating inedges spaced from said plate edges; b. means for retaining said modulesin position on said structure portion; and c. adjacent modules beingdisposed with their terminal edges in compressive abutting relationshipestablishing an interfering fit between said terminal edges and therebyeffectively sealing the seams between adjacent modules while minimizingthe transmission of shear loads between the modules.
 9. Insulation asdefined in claim 8, said modules being self-supporting and includingmeans for holding said core sheets and said faceplates in assembledrelationship, said holding means permitting relative movement betweensaid plates and said core sheets in planes parallel to said sheets andpreventing movement therebetween in a direction perpendicular to saidplanes and said faceplates.
 10. Insulation as defined in claim 8,wherein said core sheets are of metal foil.
 11. Insulation as defined inclaim 8, wherein the stack of core sheets includes corrugated coresheets and flat core sheets separating said corrugated core sheeTs andcooperating with the corrugations therein to divide the spaces betweenadjacent sheets into small, substantially mutually isolated spaces.